The United States of America has enlisted commercial planes to help with the evacuation of people from Afghanistan.
A Pentagon statement said the 18 aircraft would not fly to Kabul, but would instead help move people transiting in third countries.
Many thousands of Afghans are crowded outside Kabul airport, desperate to flee the country after the Taliban swept to power last week.
At least 20 people have died, a Nato official told Reuters news agency.
But reports suggest the scene is calmer on Sunday than in previous days.
UK armed forces minister James Heappey said the Taliban were now marshalling people into queues at Hamid Karzai International Airport, making the process faster for those hoping to leave.
The UK has airlifted out more than 1,700 people in the past 24 hours, he said, as the situation had improved.
The day before, Sky News’s chief correspondent Stuart Ramsay said that people at the front of the crowd of thousands outside the airport were being “crushed to death”, with British soldiers pulling those in most danger from the throng.
On Sunday, the US Department of Defense announced the activation of the Civil Reserve Air Fleet (CRAF) to help with the evacuation.
This allows the US to mobilise civilian airlines to help in an emergency. It was last used ahead of, and during, the US invasion of Iraq in 2003 and the Gulf War of 1990-1991.
According to the statement, the level one activation is for 18 planes: four from United Airlines; three each from American Airlines, Atlas Air, Delta Air Lines and Omni Air; and two from Hawaiian Airlines.
“Activating CRAF increases passenger movement beyond organic capability and allows military aircraft to focus on operations in and out of Kabul,” it read.